树脂富集铼的研究

用201×7强碱性凝胶型离子交换树脂对钼精矿焙烧烟尘浸出液中的铼进行分离富集工艺条件进行研究。通过对溶液中主要金属离子存在状态的分析,选择用201×7树脂对溶液中铼进行离子交换吸附,对该树脂在实验溶液中的有关吸附交换的表观吸附容量、吸附溶液pH等进行了实验研究,另外选择出了对负载树脂上铼进行有效解吸的解吸剂,并进行了动态解吸。实验结果表明:烟尘浸出液经氧化预处理后,用201×7树脂在常温,pH=9.0时可以对浸出液中的铼有效富集,树脂对铼的表观饱和吸附容量为92 mg/g;采用1 mol/L的硝酸溶液可以对负载树脂上的铼进行有效的解吸。     

Sorption of rhenium and vanadium from mineralized solutions by fibrous ionites

Sorption of rhenium(VII) and vanadium(V) from mineralized sulfate-chloride solutions by fibrous ionites of the FIBAN series is investigated. Equilibrium, kinetic, and dynamic characteristics of sorption of Re and V by the FIBAN ionite of the AK-22 brand, which contains functional groups =NH₂, -NH₂, -COOH, and ≡N, are found. It is established that the maximal capacity of this reagent in regards to vanadium(V) is observed at pH = 4. Sorption isotherms of Re and V are linear, being described by the Henry equation with constants K _H = 1.36 ± 0.30 dm³/g (R ² = 0.995) and 674 ± 21 cm³/g (R ² = 0.999), respectively. Integral sorption kinetic curves are found under conditions of a limited solution volume, and effective diffusion coefficients of Re and V, which constituted 9.0 × 10^?13 and 7.5 × 10^?15 m²/s, respectively, are calculated allowing for the half-transformation time. The possibility of separating these metals in dynamic conditions is shown.     

An increase in purity of ammonium perrhenate solutions with respect to molybdenum(IV) with the sorption recovery of rhenium(VII) from Mo-containing solutions

The possibility of the additional purification of ammonia rhenium desorbates with respect to molybdenum in the course of the sorption recovery of rhenium from Mo-containing solutions with the help of Purolite A170 and Purolite A172 weak base anion-exchange resins is considered. The pH-dependence of sorption of Re(VII) and Mo(VI) on these anion-exchange resins is investigated in static conditions with the 1 M (NH₄)₂SO₄ background in the solution. It is shown that the range of pH, in which anion-exchange resins retain the ability to sorb Re(VII), is also spread to a weakly basic region. A substantial decrease in the adsorption of Re(VII) starts already with an increase in pH above 7.5. The capacity of anion-exchange resins with respect to Mo(VI) starts to decrease noticeably with an increase in pH of solutions above 5.0, and molybdenum almost ceases to sorb by both anion-exchange resins upon reaching pH ~ 7.0. In order to decrease the Mo(VI) content in rhenium desorbates with the sorption recovery of Re(VII) from Mo-containing solutions on weak base anion-exchange resins, the following flowsheet is suggested. Initially, the main amount of sorbed Mo(VI) is desorbed by contacting the saturated anion-exchange resin with the ammonium sulfate solution upon mixture stirring and holding constant pH of the solution in limits of 7.0–7.5 due to the addition of dosed amounts of ammonia solution. Then anion-exchange resin is separated from the ammonium sulfate solution containing Mo(VI), washed with water, and Re(VII) is desorbed by ammonium solution in dynamic conditions. The verification of the proposed method for the resins saturated by sorption from the model solution of the composition, g/L, 98 H₂SO₄, 4 Mo(VI), and 0.5 Re(VII) showed the occurrence of desorption of no less than 90% sorbed molybdenum during the treatment of anion-exchange resins with ammonium sulfate solution. Herewith, concentration ratio Re(VII) : Mo(VI) in ammoniacal rhenium desorbates when using A170 anion-exchange resin increases 11-fold and when using A172 anion-exchange resin, it increases 20-fold compared with that attained without the additional washing of Mo(VI). Losses of Re(VII) with the Mo-containing desorbate (reversible) do not exceed 5.2% of the amount of sorbed Re(VII).     

Sorption behaviour and mechanism of ytterbium(III) on imino-diacetic acid resin

The sorption behaviour and mechanism of a novel chelate resin, imino-diacetic acid resin (IDAAR), for Yb(III) has been investigated in HAc–NaAc medium. The sorption of Yb(III) obeys the Freundlich isotherm. Optimum sorption for Yb(III) on IDAAR is at pH 5.13 and the statically saturated sorption capacity is 187 mg/g resin at 298 K. Yb(III) can be eluted using 1~2 mol L^− 1 HCl and the resin can be regenerated and reused without apparent decrease of sorption capacity. The apparent sorption rate constant is k₂₉₈ = 1.57 × 10^− 5 s^− 1; the apparent activation energy is 13.8 kJ mol^− 1 and the enthalpy change ΔH of IDAAR for Yb(III) is 29.8 kJ mol^− 1. The sorption mechanism of IDAAR for Yb(III) was examined by using chemical methods and IR spectrometry. The molar coordination ratio of the functional group of IDAAR to Yb(III) is 3:1 with the coordination compound formed between oxygen atoms in the functional group of IDAAR and Yb(III).     

Sorption extraction of cobalt ions from nitrate media by the iminodiacetate chelating resins Lewatit TR-207 and TR-260

Cobalt-ion sorption from nitrate media by the macroporous chelating resins Lewatit TR-207 and TR-260, which contain active functional groups based on iminodiacetic acid, is studied. Both resins are shown to sorb cobalt from nitrate solutions rather efficiently at pH 1.5–2.0, and the degree of cobalt extraction reaches ～100% for a solid to liquid ratio of ≥0.3. Under optimal conditions, the cobalt capacity of the resins is ～160 mg/g. The system under study is equilibrated within 240 min, and >70% Co is extracted during the first hour of sorption. On heating to 40–40°C, cobalt sorption enhances; however, upon further heating to 50–52°C, the extraction of cobalt decreases, which is probably caused by thermal destruction of the resin. The estimated change in the enthalpy of cobalt sorption in the temperature range 21–41°C is about +84 kJ/mol. The results obtained are employed to test the cobalt sorption under dynamic conditions in a laboratory column packed with Lewatit TR-207 resin in the H⁺ form (the working volume of the column is 100 ml) using the real mother liquor (24.5 mg Co/l) of cobalt oxalate precipitation. Quantitative desorption of cobalt is conducted with a solution of HNO₃ (400 g/l). During dynamic tests, about nine specific volumes of the initial mother liquor are passed through the column. After this, the cobalt content in the purified solution is lower than 0.4–0.5 mg/l; i.e., the total degree of cobalt extraction is >98%. In the desorption solution, the cobalt concentration increases to ～0.3 g/l, which corresponds to a more than tenfold degree of cobalt enrichment. Thus, the resins under study can be recommended for the extraction of cobalt microamounts (20–50 mg/l) from foul and reused waters.     

The effect of strain rate and depressed temperature on the low cycle deformation behavior of alpha iron

The low cycle deformation saturation stress in Ferrovac-E a-iron was studied using diametral plastic strain (0.001 ≤ Δε_dp/2 ≤ 0.0135) as the control variable. Increasing strain rate (6 × 10^•5 s^•1 • 4 × 10^•3 s^•1) and decreasing temperature (295 to 173 K) increased the saturation stress levels. The cyclic work hardening coefficient decreased from 0.18 at 295 K to 0.10 at 173 K, which is consistent with previous studies of monotonie deformation. The temperature dependence of both the saturation stress and the strain rate sensitivity, as measured during cyclic deformation, were similar to that measured during monotonic tensile tests. The temperature dependence of the dislocation velocity indexm* was in good agreement with published values from high cycle fatigue and monotonie tensile tests. Thus the same deformation mechanisms are believed to occur in both monotonie and large plastic cyclic deformation (Δε_dp/2 ≥ 0.001) of a-iron.     

Chemical precipitation of copper from copper–zinc solutions onto selective sorbents

The selective sorption and multiple concentration of copper in the form of an ultradisperse precipitate from a diluted Cu²⁺–Zn²⁺-solution has been investigated. The selective sorption is accomplished by means of weakly basic anion exchangers in their free base forms. Regeneration of the sorbent and conversion of Cu²⁺ to Cu⁰ is carried out by means of a chemical reduction in the resin phase. Thus the resins can be reused for sorption of further copper ions. The process has been investigated in both, batch and packed bed experiments. After multiple saturation–reduction cycles an accumulation of metallic copper on the surface and in the pores of the sorbent is observed. The presence of finely dispersed metallic copper leads to the additional sorption of the Cu²⁺ ions due to a synproportional reduction–oxidation reaction. The total uptake of copper after several cycles amounts to more than 300 % of the anion exchange capacity.     

Uranium sorption from phosphoric acid solutions using selective ion exchange resins: Part II. Kinetic studies

Experiments have shown that the sorption of uranium from strong phosphoric acid solutions onto four D2EHPA/TOPO based ion exchange resins and one aminophosphonic acid resin is particle diffusion controlled in the uranium concentration range 42–780 μM. Interdiffusion coefficients of about 10^?12 m²s^?1 were obtained for D2EHPA/TOPO resins and 0.14 × 10^?12 m²s^?1 with the aminophosphonic acid exchanger at 20°C in 3 M H₃PO₄. Both homogeneous particle diffusion, based on Fick's Law, and the ash layer diffusion model fitted the kinetic measurements.     

Rate analysis of sorption of Ce3+, Sm3+, and Yb3+ ions from aqueous solution using Dowex 50W-X8 as a sorbent in a continuous flow reactor

Kinetic analysis of removal of three rare earth elements metals, Ce³⁺, Sm³⁺, and Yb³⁺ ions from aqueous solutions in a continuous flow fixed bed reactor using Dowex 50W-X8 ion-exchange resin was conducted. The performance of the fixed bed sorption was evaluated using the concept of the sorption breakthrough process. Parameters characteristic of a fixed bed sorption such as breakthrough times, saturation times, critical reactor lengths, and lengths of mass transfer zone were inferred from the metal ion concentration breakthrough curves. The sorption capacity of Dowex 50W-X8 ion-exchange resin for Ce³⁺, Sm³⁺, and Yb³⁺ are 191, 252, and 294 mg/g, respectively. The sorption kinetics were evaluated using a zero-order, first-order and second-order reaction models. The kinetics of the sorption process follows a zero-order model which has not been reported before. The rate constants of sorption using the zero-order kinetic model are obtained. Two different analysis were conducted to identify whether the diffusion is intraparticle or film diffusion. Both analysis confirms that the film diffusion is the controlling mechanism in reactor bed.     

Thermodynamic properties of holmium monogermanide

The heat capacity and enthalpy of HoGe is investigated for the first time over a temperature range between 51.62 and 2096 K. The values of heat capacity, entropy, reduced Gibbs energy (J · mole^?1 × × K^?1), and enthalpy (J · mole^?1) are determined at 298.15 K: C °_P(T) = 49.63 ± 0.20; S °(T) = 89.1 ± 0.7; Φ′(T) = 50.9 ± 0.8; H °(T) ? H °(0 K) = 11391 ± 57. Temperature dependences of enthalpy (J · mole^?1) for holmium monogermanide are determined as follows: H °(T) ? H °(298.15 K) = 8.474 × × 10^?3 · T² + 47.13 · T + 226747 · T^?1 ? 15565 and H °(T) ? H °(298.15 K) = 88.91 · T ? 26507, for 298.15–1765 K and 1951–2096 K, respectively. The enthalpy and entropy of HoGe melting are calculated: T_m = 1765 ± 35 K, ΔH_m = 36.3 ± 2.9 kJ · mole^?1, ΔS_m = 20.5 ± 1.6 J · mole^?1 · K^?1.     

Diffusion and electrotransport of some transition elements in (b.c.c.) thorium

Diffusion and electrotransport parameters of the transition elements molybdenum, rhenium, tungsten and zirconium in β thorium were measured, for the temperature range 1660–1945 K. For each solute element, except zirconium, the measurement was made at four different temperatures, where as for zirconium, studies were performed for only two temperatures 1770 and 1870K. Our results indicate that all four solute elements migrate to the anode in b.c.c. thorium with mean Z¹ values of −6.6 for Mo, −4.6 for Re, −8.2 for W and about −2.5 for Zr. The results also indicate that molybdenum, rhenium and tungsten diffuse much faster in β thorium than zirconium which suggests a correlation between solute atom electric mobility and diffusivity with the atomic sizes of both the solute and matrix atom. Results of the diffusion studies yield the following equations of diffusion for Molybdenum: D_Mo = 15.1 exp(−51,500/RT) Renium: D_Re = 4.04 × 10⁻³ exp(−20,100/RT) Tungsten: D_W = 0.103 exp(−38,100/RT) Zirconium: D_Zr = 1.70 × 10⁴ exp(−91,700/RT).     

Study on sorption of D155 resin for gadolinium

The sorption behavior and mechanism of a Macroporous weak acid resin, （D155 resin,） for Gd（Ⅲ） were investigated. The statically saturated sorption capacity is 283 mg/g resin at 298 K in HAc-NaAc medium. The Gd（Ⅲ） adsorbed on macroporous weak acid resin, （D155 resin,） could be reductively eluted with the mixed solution of HCl and NaCl, and the elution percentage was as high as 100%. The resin could be regenerated and reused without remarkable decrease in sorption capacity. The apparent sorption rate constant was k298=1.98×10^5 s^-1. The apparent activation energy was Ea=2.78 kJ/mol. The sorption behavior of D155 resin for Gd（Ⅲ） obeyed the Langmuir isotherm. The thermodynamic sorption parameters were △H=33.0 kJ/mol,△S=192 J/mol/K, and △G298=-24.3 kJ/mol. The sorption mechanism of D155 resin for Gd（Ⅲ） was examined by using chemical method and IR spectrometry. The coordination compound was formed between oxygen atoms in the functional group of D155 resin and Gd （Ⅲ）.     

Study of sorption purification of lithium hydroxide solutions from aluminum by resin ANB-11g

The results of studying the main regularities of the sorption of aluminum on complexing resin ANB-11g from lithium hydroxide solutions are given. The sorbent contains functional groups of methylglucosylamine (N-methylglucamine) and is produced by amination of chloromethylated copolymer of styrene and divinylbenzene by methylglucosylamine. Tests of its chemical and thermal stability in solutions containing 48 g/dm³ LiOH showed that ANB-11g retains sorption properties after 30 days contact with it. Heating of the studied sorbent in this solution to 373 K doesn’t lead to a change in IR spectra-they are identical to the original. It was established on constructing the sorption isotherms of aluminum from solutions with 12–96 g/dm³ LiOH that an increase of the resin’s capacity for aluminum is observed with increasing content of the alkali in the original solution. The sorbent is regenerated by a diluted solution of the alkali with heating of the eluent to T = 323–363 K. As a result of pilot industrial testing of sorption purification of lithium hydroxide solutions to remove aluminum, the content of metal in them decreased by 1–2 orders of magnitude in them depending on the volume of solutions that passed through the resin. The degree of aluminum desorption was 99.5%.     

Removal of SO2 with oxygen in the presence of Fe(III)

A laboratory study of the aqueous oxidation of SO₂ in the presence of Fe(III) and Fe(II) has been conducted. The SO₂ concentration was 3930 ppm (3.93 × 10⁻³ atm or 398 Pa) in a gas stream with nitrogen and oxygen. The oxygen pressure was varied from 0 to 0.203 atmosphere. The initial concentration of Fe(III) ranged from 10⁻³ to 5-10⁻³ molar while that of Fe(II) was 5 × 10⁻³ molar. The temperatures were 298, 309.2, and 317.5 K. The solution pH was 1.83. The oxidation of SO₂ is intensive and yields from 90 to 97 pct recovery of incoming SO₂ when 5 × 10⁻³ molar Fe(III) and an oxygen pressure above 0.057 atmosphere are applied at 298 K. The reaction mechanism has been explained by determining the rate constants of the oxidation reactions from a kinetic model. The rate constants show that SO₂ is mostly oxidized by oxygen through formation of ferric-sulfite complex and that regeneration of ferric ion is possible under a normal oxygen pressure. The activation energy of the oxidation has been determined and has been found to be 13.5 Kcal/mole.     

Numerical simulation of solidification structure of high carbon SWRH77B billet based on the CAFE method

Abstract

Based on the coupled method of cellular automaton (CA) and finite element (FE), the solidification structure of 160×160 mm cast billet of high carbon SWRH77B steel was simulated. The nucleation density, kinetics of the dendrite tip growth, crystallographic orientation and coupling of CA and FE methods are discussed. In the current study, the influence of superheat on the solidification structure of the billet is researched in detail. The results show that for an increase in superheat extent from 20 to 30°C, the density of grain in billet decreased from 4·662×10⁶ to 3·087×10⁶ m^?2, and the grain mean radius increased from 295·1 to 346·3 μm. The three-dimensional microstructure of high carbon SWRH77B steel was simulated by the CAFE method, and there was good agreement with the results from industrial billet.     

Carburizing of Duplex Stainless Steel (DSS) Under Compression Superplastic Deformation

A new surface carburizing technique which combines superplastic deformation with superplastic carburizing (SPC) is introduced. SPC was conducted on duplex stainless steel under compression mode at a fixed 0.5?height reduction strain rates ranging from 6.25?×?10^?5?to 1?×?10^?3?s^?1?and temperature ranging from 1173?K to 1248?K (900?°C to 975?°C). The results are compared with those from conventional and non-superplastic carburizing. The results show that thick hard carburized layers are formed at a much faster rate compared with the other two processes. A more gradual hardness transition from the surface to the substrate is also obtained. The highest carburized layer thickness and surface hardness are attained under SPC process at 1248?K (975?°C) and 6.25?×?10^?5?s^?1?with a value of (218.3?±?0.5)???m and (1581.0?±?5.0) HV respectively. Other than that, SPC also has the highest scratch resistance.     

Uranium sorption from phosphoric acid solutions using selective ion exchange resins: Part I. Isotherms of extraction and desorption

Experimental measurements have been made of the isotherms for the sorption and desorption of uranium from synthetic phosphoric acid solutions with two types of cation exchange resin. Work was performed with several D2EHPA/TOPO impregnated resins and with one commercially available ion exchange resin containing aminophosphonic acid groups. The effect of Fe²⁺, Fe³⁺ and Ca²⁺ on the effective capacity has been examined. Results show that D2EHPA/TOPO resins are n not affected by the presence of Fe²⁺ or of Ca²⁺. Ferrous ion, whichreduces uranium to the tetravalent oxidation state, prevents uranium sorption. The resin containing aminophosphonic acid groups possesses a higher effective capacity than D2EHPA/TOPO-based resins and was also not affected by the presence of Ca²⁺. Ferric and ferrous ions reduce the effective capacity considerably, though the resin still extracts U(IV).D2EHPA/TOPO-based resins can be eluted with 3 M H₃PO₄ at 40°C or 3 M H₃PO₄ solutions containing Fe²⁺. Ammonium carbonate was found to leach the organic extractants from the resin. The aminophosphonic acid resin can be eluted with (NH₄)₂CO₃ at 20°C producing eluate solutions highly enriched in uranium. A conceptual flowsheet for uranium recovery is proposed.     

Mechanism of Dynamic Strain Aging in a Niobium-Stabilized Austenitic Stainless Steel

Dynamic strain aging (DSA) behavior of a niobium (Nb)-stabilized austenitic stainless steel (TP347H) was studied from room temperature (RT) to 973 K via tensile testing, transmission electron microscopy (TEM), and internal friction (IF) measurements. The DSA effect is nearly negligible from 573 K to 673 K, and it becomes significant at temperatures between 773 K and 873 K with strain rates of 3 × 10^?3 s^?1, 8 × 10^?4 s^?1, and 8 × 10^?5 s^?1, respectively. The results indicate that a dislocation planar slip is dominant in the strong DSA regime. The Snoek-like peak located at 625 K is highly sensitive to the diffusion of free carbon (C) atoms in solid solution. C-Nb octahedrons are formed by C chemical affinity to substitutional Nb solute atoms. Octahedron structure is very stable and captures most free C atoms and inhibits DSA at low tensile test temperatures of 573 K to 673 K. At high test temperatures in the range from 773 K to 873 K, C-Nb octahedrons break up and release free C and Nb atoms, resulting in the stronger Snoek-like peak. The interaction between C atoms and dislocations is responsible for DSA at low temperatures ranging from 573 K to 673 K. At higher temperature of 773 K to 873 K, the Cr and Nb atoms lock the dislocations, and this formation contributes to DSA.     

Gasification Characteristics and Kinetics of Coke with Chlorine Addition

The gasification process of metallurgical coke with 0, 1.122, 3.190, and 7.132 wt pct chlorine was investigated through thermogravimetric method from ambient temperature to 1593 K (1320 °C) in purified CO₂ atmosphere. The variations in the temperature parameters that T _i decreases gradually with increasing chlorine, T _f and T _max first decrease and then increase, but both in a downward trend indicated that the coke gasification process was catalyzed by the chlorine addition. Then the kinetic model of the chlorine-containing coke gasification was obtained through the advanced determination of the average apparent activation energy, the optimal reaction model, and the pre-exponential factor. The average apparent activation energies were 182.962, 118.525, 139.632, and 111.953 kJ/mol, respectively, which were in the same decreasing trend with the temperature parameters analyzed by the thermogravimetric method. It was also demonstrated that the coke gasification process was catalyzed by chlorine. The optimal kinetic model to describe the gasification process of chlorine-containing coke was the ?esták Berggren model using Málek’s method, and the pre-exponential factors were 6.688 × 10⁵, 2.786 × 10³, 1.782 × 10⁴, and 1.324 × 10³ min^?1, respectively. The predictions of chlorine-containing coke gasification from the ?esták Berggren model were well fitted with the experimental data.     

Electrode process of La(III) in molten LiCl-KCl

The electrode process of La(III) at Mo electrode in the molten LiCl-KCl for temperatures ranging from 683 K to 773 K was studied by cyclic voltammetry and chronopotentiometry, respectively. The results showed that in the molten LiCl-KCl, reduction of La(III) occurred in a step with a global exchange of three electrons. Cyclic voltammetry studies indicated that at a sweep rate lower than 0.2 V/s, the electroreduction of La(III) to lanthanum metal was reversible and controlled by diffusion of La(III). However, the process became under a mixed control of both diffusion and electron transfer when sweep rate exceeded 0.2 V/s. And an empirical temperature dependence of the diffusion coefficient of La(III) was proposed: lnD_La(III)=7.742–1.441×10⁴/T. And the relation between the formal potential of La(III)/La versus Ag/AgCl reference electrode and temperature was described in the following equation: E^θ'=–1.402–4.689×10²/T.